Kleihauer–Betke test

Kleihauer

KB stain, annotated

Kleihauer–Betke test (KBT), also known as the Kleihauer–Betke (KB) stain, is a blood test used to measure the presence of fetal hemoglobin (HbF) in the maternal blood circulation following pregnancy or childbirth. This test is particularly important in cases of suspected fetal-maternal hemorrhage (FMH), where it helps in assessing the extent of blood mixing between the mother and fetus. The Kleihauer–Betke test is a critical tool in the management of Rh-negative mothers to prevent Rh disease in future pregnancies.

Procedure

The Kleihauer–Betke test involves staining a sample of the mother's blood with an acid solution that elutes the adult hemoglobin but leaves the fetal hemoglobin intact. This difference allows for the visualization and quantification of fetal red blood cells (RBCs) against the background of maternal cells. The presence of these fetal cells is indicative of a fetal-maternal hemorrhage. The number of fetal cells is then used to calculate the volume of fetal blood that has entered the maternal circulation, which is crucial for determining the appropriate dosage of Rho(D) Immune Globulin (RhIG) to be administered to Rh-negative mothers.

Clinical Significance

The primary application of the Kleihauer–Betke test is in the postpartum management of Rh-negative women. If fetal RBCs are detected in the maternal blood, it indicates that the mother has been exposed to Rh-positive blood, posing a risk of developing antibodies against Rh-positive blood cells. This condition, if left untreated, can lead to complications in subsequent pregnancies, such as hemolytic disease of the newborn (HDN). Administering RhIG based on the results of the KBT can prevent the mother from producing anti-Rh antibodies, thereby protecting future pregnancies.

Additionally, the Kleihauer–Betke test can be used in the assessment of FMH in cases of abdominal trauma during pregnancy, miscarriage, or stillbirth, where it aids in evaluating the risk of sensitization and the need for RhIG prophylaxis.

Limitations

While the Kleihauer–Betke test is valuable, it has limitations. The test requires manual counting of cells, which can be subject to inter-observer variability. Moreover, it may not detect very small volumes of fetal-maternal hemorrhage, and there are conditions, such as the presence of fetal-maternal microchimerism, that can affect its accuracy. Advances in technology have led to the development of alternative methods, such as flow cytometry, which can offer more precise quantification of fetal cells in maternal blood.

Conclusion

The Kleihauer–Betke test remains a cornerstone in the management of Rh-negative women post-delivery or after events that could lead to fetal-maternal hemorrhage. Despite its limitations, it plays a crucial role in preventing Rh disease and ensuring the well-being of both mother and future pregnancies. As medical technology advances, it may be supplemented or replaced by more precise methods, but its principle will continue to be relevant in obstetric care.

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